Update README - mention HTTP protocol usable only with database/sql…

… interface (#1160)

README.md

@@ -181,7 +181,7 @@ clickhouse://username:password@host1:9000,host2:9000/database?dial_timeout=200ms
 
 The native format can be used over the HTTP protocol. This is useful in scenarios where users need to proxy traffic e.g. using [ChProxy](https://www.chproxy.org/) or via load balancers.
 
-This can be achieved by modifying the DSN to specify the http protocol.
+This can be achieved by modifying the DSN to specify the HTTP protocol.
 
 ```sh
 http://host1:8123,host2:8123/database?dial_timeout=200ms&max_execution_time=60
@@ -208,6 +208,8 @@ conn := clickhouse.OpenDB(&clickhouse.Options{
 })
 ```
 
+**Note**: using HTTP protocol is possible only with `database/sql` interface.
+
 ## Compression
 
 ZSTD/LZ4 compression is supported over native and http protocols. This is performed column by column at a block level and is only used for inserts. Compression buffer size is set as `MaxCompressionBuffer` option.